Checkweighing of glass bottles is important in that overweight bottles involve a waste of glass, and hold less liquid than they should. Underweight bottles contain more liquid than they should. Some glass forming processes require positive displacement of a known volume of glass to produce containers. Variations in weight change the volume of glass and many defects may result therefrom.
A known method of checkweighing involves manually removing one or two hot bottles from a conveyor perhaps three times an hour, weighing them, likewise manually, and then (frequently) discarding the weighed bottles since it is inconvenient to return them to the conveyor for transfer to the lehr.
Underweight or overweight bottles are an indication for appropriate adjustment of the gobs on the molding machines which dispense the molten glass to the molds.
Another known method of checkweighing involves an automatic weighing machine usually disposed on or adjacent to a molding machine. These known weighing machines suffer from two main disadvantages. Firstly, when a container is removed from a continuous flow of closely spaced hot glass bottles, no difficulty in product handling is encountered until after the weighing operation. At that point in time, product handling becomes a serious problem since another container must be removed from the flow of bottles to make room for the weighed container to be inserted in the flow. This manipulation has proven to be very difficult because of the speed and temperatures involved. Secondly, they are subject to the very heavy vibration of the molding or conveying machinery, and thirdly, the hot glass bottle is very close to the balance mechanism and is subjected to strong air currents in its immediate environment. All of these effects militate against accurate weighing.
The present invention seeks to overcome the above defects by providing weighing apparatus in which the hot glass bottle is isolated from vibrating machinery while it is being weighed, and in which the hot glass bottle is remote from the more sensitive elements of the weighing apparatus and is subjected to negligible air currents. Moreover, the present invention permits the bottles, after weighing, to continue in the transfer path to the lehr for annealing, thus avoiding bottle wastage.